Plastic extrusions having flexible elements are used for making a variety of structures such as hinges or weather-stripping. Such extrusions typically comprise a thin flexible section adjoining two thicker, fairly rigid sections which may be fastened or affixed to other structures. The entire extrusion is commonly made from polypropylene material.
These extrusions, however, have been less than adequate when subjected to a large number of flexure cycles, especially in low temperature environments. This is because the thin flexible section usually fails by fatiguing or tearing away from one of the rigid sections.
An attempt has been made to address this flexure cycle problem in U.S. Pat. No. 4,563,381. This patent discloses an extrusion comprising a flexible section made from a polyester elastomer extruded in tandem (coextruded) with at least one semi-rigid section of a thermoplastic material. During the coextrusion process, the end surfaces of the flexible section bond to surfaces of the rigid sections.
Unfortunately, the thin flexible section tends to peel away from the rigid sections when subjected to repeated flexing. Accordingly, there is still a need for an improved extrusion having a thin flexible section that is securely connected to one or more rigid sections.